Glitch with steam recording and modded STS

[The_One_Tumbleweed_Rolls_By]

I adore modded sts and have been playing nothing else for the past week. I migrated to steam after Christmas from the switch, so i've been playing for a while before I dove into mods. Despite the fact that I have no youtube channel and thus no way of sharing videos on steam easily, I enjoy saving videos of cool things that happen when I play. When I view other people play STS, I noticed I like watching sped up runs, because the monotony of watching someone decide whether to play a certain card in one combat bores me. My plan was therefore to save my own recordings and then speed them up using a video editor if I had a cool run.

Unfortunately, Steam refuses to record any data from my modded STS, so I can't do this. Is this a permanent problem that is widespread across modded games, or is there something I can do to debug it. I am not worried about completely clearing my progress if that would help, since I have yet to earn any achievements on steam and am using the unlock everything mod. One final clarification is that steam records me opening the mod manager, where one can select which mods to activate before actually booting up the game. After that it knows that I played slay the spire, but it doesn't save any video or audio. Is there anything I can do?